Metering- reflectivity vs tone? (i.e. black objects in shadow)

So question about metering
I know meters are tuned for midtones and thus, something darker than midtone will reflect less light and lead to overexposure and vice versa and you thus compensate accordingly

I also know that according to Zone system techniques, that you can place highlights in approx +2 for slide (meter highlights and open 2 stops) and the darkest part you want details in (shadows) in -2 (meter shadows and close down 2)

But what happens if that highlight is dark toned (if that makes sense? i.e. black detail being rim or edge lit)

GarageBoy and others who may not be familiar with it,
A frequent APUG forum contributor Ralph Lambrecht has coauthored a book "Way Beyond Monochrome" that is a comprehensive reference on black and white photography and well worth adding to your library. Among all the detailed information, you can find how to build a zone dial.(pages 468-469)

You take your reflected light reading from the area you are interested in, and then adjust the exposure to give you the tone you are looking for.

The challenge may be actually limiting the area read to what you want to evaluate.

Matt

“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”

Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2

Spot meters are reflective meters, but their narrow angle of view (typically 1° to 5°) means they are excellent for isolating specific areas — as Matt King said in his second sentence, "actually limiting the area read to what you want to evaluate", or put another way, analysing all principal luminances, in the first instance not assuming the scene presented before you or the meter is "average".